One known form of theft-resistant sign bracket is a bracket comprising an elongated element molded from a synthetic resin. A bolt extends through an elongated slot in the molded element and is engaged with a nut located in a nut-receiving space within the molded element, the nut-receiving space being elongated along the direction of elongation of the slot. The nut is slidable in the direction of elongation of the slot but restrained against rotation by opposed internal walls of the nut-receiving space. The bolt is a “one-way” bolt, having a receptacle formed in its head for receiving the tip of a screwdriver. The receptacle is formed with surfaces configured to allow clockwise rotation of the bolt by the screwdriver but to deflect the screwdriver axially outward from the receptacle when the screwdriver is rotated counterclockwise. End slots, formed in opposed ends of the elongated molded element, are engageable with lengths of fence wire on opposite sides of an opening of a chain link fence and a wall of at least one of the end slots is provided with a hole for a screw or similar fastener used to maintain engagement of that end slot with the length of fence wire extending through it.
In a typical sign installation, four such brackets are attached to the chain link fence in positions such that the bolt of each bracket can be aligned with one of the holes in a sign to be attached to the fence. The elongation of the slot, and the movability of the bolt in the direction of elongation of the slot and the elongated nut-receiving space, allow the bracket to be adjusted to accommodate variations in the positions of the bolt holes in the sign.
The brackets and the bolt holes in the sign are typically located inboard relative to the edges of the sign to make access to the brackets difficult after the bolts are tightened. Thus the sign can be secured to a chain link fence in such a way that a thief not equipped with special tools will encounter a considerable amount of difficulty in attempting to remove the sign.
The bracket described above is suitable for use with chain link fences. However, in recent years, so-called, “high security” or “ballistic” fences have come into widespread use to protect equipment such as electric substation transformers and the like by preventing damage to the equipment by bullets and other projectiles.
A typical ballistic fence includes a unitary layer of heavy-gauge steel formed with an array of horizontally elongated undulating strips extending parallel to one another. The undulations of adjacent strips are offset from one another so that parallel columns of narrow, horizontally elongated, slots are formed in the heavy-gauge steel layer.
The unitary layer of steel formed with undulating strips and horizontally elongated slots is typically welded to, and reinforced by, a mesh of horizontally- and vertically-extending, heavy-gauge steel wires. The unitary layer of steel forms an outer face of the fence, and the mesh of steel wires forms an inner face of the fence.
The bracket described above, which is designed for use with chain link fences, cannot be fitted to a ballistic fence in a manner similar to the manner in which it is fitted to a chain link fence. That is, the end slots in the elongated molded element cannot be readily engaged with the undulations of the ballistic fence.
There has been a need for a sign bracket having a capability of bolt-position adjustment similar to that of the sign bracket designed for chain link fencing, and also having the capability of secure attachment to a ballistic fence.